| Compositing for high performance insulation materials has become an inevitable trend,and numerical method is one of the most effective means to predict thermal properties of composites.This paper investigated on hollow glass microsphere/epoxy composites system,and numerical calculation method,performance prediction on thermal insulation properties as well as component ratio of composites were discussed,in order to serve for the surface insulation of large concrete structures in the South-to-North Water Diversion Project.Since the hollow glass microsphere is a two-phase material(glass,air)and its size is very small,which has brought great difficulties to the establishment of a numerical model.Therefore,how to homogenize the HGM is the key to predict the thermal conductivity of high-filled hollow glass microsphere/epoxy composites.Three-phase(epoxy,glass and air)model and two-phase(epoxy and homogenized hollow glass microsphere)model were established,respectively,and the effective thermal conductivity of HGM is obtained through the two equivalents.Then,the thermal conductivity of high-filled composites was studied by simulation and experiment,the influence of various factors on thermal conductivity of composites material was also analyzed.Finally,composites properties such as viscosity,thermal expansion coefficient,bond strength and tensile strength were tested with the variety of composition.All the work lied a solid foundation for the design and preparation of thermal insulation composites.The main results of this paper are as follows:(1)Hollow glass microsphere homogenization treatment method was studied,and the effective thermal conductivity of hollow glass microsphere was obtained.Aiming at the uniform and non-interacting characteristics of hollow glass microsphere in low-filled composites,random sequence adsorption algorithm was used to establish three-phase and two-phase meso-scale composites model with 5% filler loading.The effective thermal conductivity of hollow glass microsphere is determined by comparing and analyzing the simulation results of heat insulation properties of the two model.In addition,the effects of model size,shell's thermal conductivity,hollow glass microsphere size and porosity on the thermal conductivity of hollow spherical materials were studied.(2)The two-phase model of the homogenized hollow glass microsphere/epoxy was established,furthermore,the thermal insulation performance of the composites material were discussed by numerical simulation analysis and experimental research.According to the distribution characteristics of hollow glass microsphere in the composites with the different loadings,composites meso-scale models with different loadings were constructed to predict the thermal insulation properties of the composites.The reliability of simulation results was verified through the comparison with the measured results.In the end,the effects of model size,filler volume fraction,and filler thermal insulation on the thermal conductivity of the composites were studied.(3)The physical and mechanical properties such as the viscosity,thermal expansion coefficient,bond strength,as well as the tensile strength of hollow glass microsphere/epoxy composites were tested,and the influence of composition ratio on properties of composites materials was analyzed.Considering the thermal insulation performance,mechanical properties and manufacturability of composites materials,the better composition ratio of hollow glass microsphere/epoxy composites was given. |
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